User defined log filename in Ada

The following compiles

with Util.Log.Loggers;

package body LogTest is

   Log : constant Util.Log.Loggers.Logger := Util.Log.Loggers.Create("./abc.log");
   ...
end LogTest;

The problem is that I need to read in the filename from a configuration file so I tried

package body LogTest is
   Log: Util.Log.Loggers.Logger;

   procedure LogTestInit(filename : String) is
   begin
      Log := Util.Log.Loggers.Create(filename);
   end LogTestInit;

but it comes up with left hand side of assignment must not be limited type. Two questions

1. What should I do if I wish to pass in the filename? How do I create the log instance.
2. Why does the assignment work in the first case but not in the second?

I've since found that the string passed in

Log : constant Util.Log.Loggers.Logger := Util.Log.Loggers.Create("./abc.log");

is not a filename but an identification tag, so it can be a hard coded constant, or, as @simonwright hinted, a function that returns a string. If there are multiple tasks or packages, each can have its own tag. The actual log filename is set in the configuration file that is passed to the Initialize function.

For C# people, limited means it is not ICloneable.

For C++ people, limited means it is a non-copyable object.